It is known that hydrogenolysis of glycerol involves first dehydration to give acetol followed by its hydrogenation to 1,2-propylene glycol (1,2-PG). In direct hydrogenation route, these steps are carried out together, however, dehydration step does not require hydrogen and also the kinetics of both these steps being different and several side products are formed. This is a major drawback of the single step hydrogenation route.
WO/2005/095536 titled “Method of producing lower alcohols from glycerol” and the thesis titled “Catalytic conversion of glycerol and sugar alcohols to value-added products” by Mohanprasad A. Dasari, chapter 4 titled “Dehydration of glycerol, to acetol via catalytic reactive distillation” discloses preparation of relatively pure hydroxyacetone from glycerol employing metallic catalysts including copper, nickel, alumina and others in the presence of water, but the selectivity of the process to hydroxyacetone is only up to 65%.
In the article “Vapor-phase reaction of polyols over copper catalysts” by Masaki Akiyama, Ryoji Takahashi, Takayoshi Hara, Kanichiro Inui and Masahiro Yokota describe the vapor-phase reaction of triols and diols over copper metal catalysts. Triols, such as 1,2,3-propanetriol (glycerol) and 1,2,3- and 1,2,4-butanetriols, are dehydrated to corresponding hydroxyketones, while 1,2-propyleneglycol is dehydrogenated to form hydroxyacetone. Supported copper as well as pure copper metal was an effective catalyst for the dehydration of glycerol to produce hydroxyacetone under inert conditions. Alumina-supported copper showed the highest catalytic activity with hydroxyacetone selectivity of >90 mol % at ambient pressure of nitrogen and at 250° C.
From prior art search results, it is clear that liquid phase selective dehydration of glycerol to hydroxyacetone resulting in 100% selectivity towards hydroxyacetone has not been successfully attempted so far. Further, dehydration of glycerol in presence of water to attain 100% selectivity to hydroxyacetone by the selective dehydration of glycerol is not documented.